Fiber Optic Surface Plasmon Resonance Research Articles

Graphene-Based Conducting Metal Oxide Coated D-Shaped Optical Fiber SPR Sensor

We report a graphene-based indium tin oxide coated surface plasmon resonance sensor built on a D-shaped optical fiber for near infrared. Different parameters of the proposed sensor have been optimized to obtain a maximal phase matching between the core guided mode and the plasmon mode using finite element method. Wavelength sensitivity of the proposed structure is as high as 5700 nm/RIU with a maximum resolution of $1.754 \times 10^{-5}$ RIU. The proposed sensor can also be used for bio layer thickness monitoring with a maximum resolution of 62.5 pm in wavelength interrogation.

A wavelength selective application for an optical fiber surface plasmon resonance sensor

In this paper, a wavelength selective optical fiber surface plasmon resonance sensor, which provides a flexible detection capability, has been experimentally investigated. The light reflected from the sensor tip in response to flowing water and ethanol are monitored at several single wavelengths. The reflected light transient modulated by flowing solvent has an exponential form, which the change in magnitude and response time are dependent on the monitoring wavelength. Optimal wavelength best suited for measurement was determined by investigating the dynamic response curve. Rather than wavelength and angular interrogation methods commonly used in SPR measurement, this single wavelength monitoring scheme is a low-cost, flexible and reliable method.

Multimode Optical Fiber Surface Plasmon Resonance Signal Processing Based on the Fourier Series Fitting

Multimode optical fiber is widely used because of its large core size, strong light-gathering ability, and remote on-line sensing ability in various environments. Due to the mode coupling and polarization loss, the signal curve obtained has wide full width at half-maximum (FWHM) and small peak value. Therefore, efficient methods to calculate the resonant wavelength are required. This paper presents a method to process the surface plasmon resonance curve (SPR) based on the Fourier series fitting. The calculated resonant wavelength is obtained with one-dimensional extremum-search method. Experiment results show the proposed method can accurately calculate the resonant wavelength of high concentration solution. Additionally, the method has higher sensitivity and is unaffected by the light source fluctuation. This method has potential value in processing the SPR signal of the multimode optical fiber.

Fiber-Optic SPR Sensor for Temperature Measurement

A fiber-optic surface plasmon resonance (SPR) sensor for temperature detection has been proposed by utilizing a thermosensitive liquid as the intermediate and combining with the fiber SPR structure. The sensing element of the sensor has been fabricated by packaging the fiber probe coated with a silver layer into a capillary filled with thermosensitive anhydrous ethanol. This packaging can protect the metal layer from oxidation and damage. Moreover, this proposed sensor achieves a sensitivity of 1.5745 nm/°C, which is much higher than that of the traditional fiber SPR sensor according to the comparative experiments.

Polydopamine-assisted fabrication of fiber-optic localized surface plasmon resonance sensor based on gold nanoparticles

A fast and facile method of fabricating fiber-optic localized surface plasmon resonance sensors based on spherical gold nanoparticles was introduced in this study. The gold nanoparticles with an average diameter of 55 nm were synthesized via the Turkevich method and were then immobilized onto the surface of an uncladded sensor probe using a polydopamine layer. To obtain a sensor probe with high sensitivity to changes in the refractive index, a set of key optimization parameters, including the sensing length, coating time of the polydopamine layer, and coating time of the gold nanoparticles, were investigated. The sensitivity of the optimized sensor probe was 522.80 nm per refractive index unit, and the probe showed distinctive wavelength shifts when the refractive index was changed from 1.328 6 to 1.398,7. When stored in deionized water at 4 °C, the sensor probe proved to be stable over a period of two weeks. The sensor also exhibited advantages, such as low cost, fast fabrication, and simple optical setup, which indicated its potential application in remote sensing and real-time detection.

Graphene Enhances the Sensitivity of Fiber-Optic Surface Plasmon Resonance Biosensor

In this paper, a fiber-optic surface plasmon resonance (SPR) biosensor is presented, in which a sheet of graphene acting as a sensing layer is coated around the gold film. A theoretical study of the proposed fiber-optic biosensor has been carried out by applying four-layer modal, which shows that by incorporating a graphene sensing layer, the sensitivity of the proposed SPR fiber biosensor can be greatly enhanced than the conventional gold film SPR fiber sensors. The relationship between resonance wavelengths and sensitivity of the proposed graphene sensing layer-based SPR fiber biosensor with the number of sensing layer has also been studied.

Performance Analysis of Bimetallic Layer With Zinc Oxide for SPR-Based Fiber Optic Sensor

We present an efficient fiber optic SPR sensor consisting of bimetallic layers of silver (Ag) and gold (Au) in coordination with zinc oxide (ZnO) for refractive-index sensing in spectral mode. The performance of the sensor is explored in terms of electric field intensity, sensitivity, and the figure of merit theoretically as well as experimentally. Four kinds of sensors with layers of Ag/ZnO, Au/ZnO, Au/Ag/ZnO, and Ag/Au/ZnO over an unclad core of the fiber are studied. For simulation, two-dimensional multilayer matrix method along with geometrical optics is used. It is found that the sensor having layers of Ag/Au/ZnO with optimized thicknesses possesses maximum electric field intensity at the interface, large shift in the resonance wavelength, sharp SPR dip, and high value of the figure of merit. In addition, the additional layers of Au and ZnO can also be used for the tuning of resonance wavelength in the visible region of the electromagnetic spectrum and for the protection of Ag layer from oxidation and; hence, can improve the durability of the sensor. Further, ZnO layer can also be used to sense some of the gases.

Fiber-optic urine specific gravity sensor based on surface plasmon resonance

A fiber-optic urine specific gravity sensor based on surface plasmon resonance is first presented in this paper. We have proposed a novel side coated Au film fiber-optic surface plasmon resonance sensor, which is much easier to fabricate than other fiber-optic surface plasmon resonance sensors, for urine specific gravity detection. We made a sensor with 48-nm thickness of sensing layer and 15-mm length of sensing region. The experimental results are satisfactory. In the urine specific gravity detection, we use wavelength and intensity modulations to extract sensing information and their detection results show good linearities. The urine specific gravity sensitivities in glycosuria detection are obtained to be 856.09nm/SG (in wavelength modulation) and 183.31%/SG (in intensity modulation), respectively. While they are ultra-high in albuminuria detection, the wavelength sensitivity is 12,645nm/SG and the intensity sensitivity is 1410%/SG.

Sensitivity enhancement of a surface plasmon resonance based fiber optic sensor utilizing platinum layer

A highly sensitive surface plasmon resonance based fiber optic sensor with platinum (Pt) layer coated on the core of the optical fiber is presented and theoretically analyzed. The sensitivity of the proposed sensor enhances linearly with the increase in the refractive index of the sensing medium for all thicknesses of Pt layers and for a given refractive index of the sensing medium, it increases with the increase in the thickness of Pt layer. 125nm thick Pt layer based fiber optic SPR sensor exhibits greatest sensitivity at high values of refractive index of the sensing medium.

Surface plasmon resonance biochemical sensor based on light guiding flexible fused silica capillary tubing

A fiber optic surface plasmon resonance (SPR) sensor based on light guiding flexible fused silica tubing with its cladding stripped and coated with gold film as SPR sensing area is presented. Theoretical simulate of the proposed sensing structure for different sensing area length and different film thickness of sensors is done to obtain the suitable parameters, and the simulation for different refractive index is carried out. Meanwhile, the experiments for refractive index (RI) measurement have been demonstrated using the developed sensor, 400μm optical fiber sensor and 125μm optical fiber sensor. Experimental results have shown the capillary sensor has advantage in terms of sensitivity and resolution. The capillary sensor is also used for detecting and monitoring biochemical binding and dissociation processes of the RNase B and Con A. It is proved that the sensor with chemical modification can be implemented for specific biochemical sensing

Surface Plasmon Resonance Biosensor Based on Smart Phone Platforms.

We demonstrate a fiber optic surface plasmon resonance (SPR) biosensor based on smart phone platforms. The light-weight optical components and sensing element are connected by optical fibers on a phone case. This SPR adaptor can be conveniently installed or removed from smart phones. The measurement, control and reference channels are illuminated by the light entering the lead-in fibers from the phone’s LED flash, while the light from the end faces of the lead-out fibers is detected by the phone’s camera. The SPR-sensing element is fabricated by a light-guiding silica capillary that is stripped off its cladding and coated with 50-nm gold film. Utilizing a smart application to extract the light intensity information from the camera images, the light intensities of each channel are recorded every 0.5 s with refractive index (RI) changes. The performance of the smart phone-based SPR platform for accurate and repeatable measurements was evaluated by detecting different concentrations of antibody binding to a functionalized sensing element, and the experiment results were validated through contrast experiments with a commercial SPR instrument. This cost-effective and portable SPR biosensor based on smart phones has many applications, such as medicine, health and environmental monitoring.

Compact multi-channel surface plasmon resonance sensor for real-time multi-analyte biosensing.

A compact multi-channel surface plasmon resonance (SPR) biosensor is demonstrated based on a tablet as the measurement platform. The SPR biosensor employs a bundle of fiber-optic SPR sensors as the multiplexed sensing elements that are illuminated by a light-emitting diode (LED) plane light source and detected by a cordless camera. The multi-channel SPR biosensor was based on optical fiber components for precise, label-free and high-throughput detection without the use of complex, specialized or fragile instrumentation that would require optical calibration. The reference and control channels compensated for the fluctuation of the LED light source and the bulk refractive index, increasing the accuracy and reliability of the biosensor. The multi-channel SPR biosensor was applied for multi-analyte biosensing of immunoglobulin G (IgG) and concanavalin A (Con A). The channels functionalized with staphylococcal protein A (SPA) and ribonuclease B (RNase B) only showed relative intensity responses to their corresponding analytes. Moreover, the multi-channel SPR sensors responded to the specific detection of IgG and Con A with an approximately linear relative intensity response to the analyte concentration. Hence, multiple analytes were simultaneously and quantitatively detected with the multi-channel SPR biosensor. This compact, cost-effective multi-channel SPR biosensor is adapted for point-of-care tests, which are important in healthcare and environmental monitoring and for biomolecular interaction analysis.

Multi-point detection of hydrogen using the hetero-core structured optical fiber hydrogen tip sensors and Pseudorandom Noise code correlation reflectometry

In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% H₂ in N₂ in the case of the 25-nm Au, 60-nm Ta₂O 5 , and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- H₂ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

Boronic acid modified fiber optic SPR sensor and its application in saccharide detection

To extend the application of fiber-optic surface plasmon resonance (SPR) sensing technology, the chemical molecular, 2-(((6-aminohexyl)(benzyl)amino)methyl) phenyl boronic acid (ABA-PBA), is prepared as the recognition monolayer and immobilized on the fiber-optic SPR probe. The boronic acid moiety in ABA-PBA monolayer can covalently bond with 1, 2- or 1, 3- diols moiety of sugar. A monolayer of ABA-PBA is assembled on the SPR sensing region and confirmed by surface enhanced Raman scattering (SERS) technique. Spectrophotometric method is used to determine the pKa of ABA-PBA. The interaction between ABA-PBA monolayer and saccharide can induce the shift of resonance wavelength. By using the miniature fiber-optic SPR sensor, saccharide concentration can be monitored in real time. It shows good selectivity to fructose at low concentrations (10–50mM).

Fibre optic surface plasmon resonance sensor system designed for smartphones.

A fibre optic surface plasmon resonance (SPR) sensor system for smartphones is reported, for the first time. The sensor was fabricated by using an easy-to-implement silver coating technique and by polishing both ends of a 400 µm optical fibre to obtain 45° end-faces. For excitation and interrogation of the SPR sensor system the flash-light and camera at the back side of the smartphone were employed, respectively. Consequently, no external electrical components are required for the operation of the sensor system developed. In a first application example a refractive index sensor was realised. The performance of the SPR sensor system was demonstrated by using different volume concentrations of glycerol solution. A sensitivity of 5.96·10(-4) refractive index units (RIU)/pixel was obtained for a refractive index (RI) range from 1.33 to 1.36. In future implementations the reported sensor system could be integrated in a cover of a smartphone or used as a low-cost, portable point-of-care diagnostic platform. Consequently it offers the potential of monitoring a large variety of environmental or point-of-care parameters in combination with smartphones.

Experimental Comparison of Fiber-Optic Surface Plasmon Resonance Sensors with Multi Metal Layers and Single Silver or Gold Layer

Fiber-optic surface plasmon resonance sensors with multi metal layers (Ti/Ag/Au) and single silver or gold layer are presented. In comparison with widely used single-layer sensors, the multi-layer sensor shows a wider refractive index measurement range (in a range of 1.3344 to 1.4111 RIU) and a better resolution in the high refractive index region (refractive index over 1.3697 RIU). In addition, the sensitivity of multi-layer sensor is between those of sensors with silver and gold layers, the chemical stability, and the film adhesion capability of multi-layer sensor are much better than those of silver layer sensor.

Fiber-Optic SPR Immunosensors Tailored To Target Epithelial Cells through Membrane Receptors.

We report, for the first time, the use of a surface plasmon resonance (SPR) fiber-optic immunosensor for selective cellular detection through membrane protein targeting. The sensor architecture lies on gold-coated tilted fiber Bragg gratings (Au-coated TFBGs) photoimprinted in the fiber core via a laser technique. TFBGs operate in the near-infrared wavelength range at ∼1550 nm, yielding optical and SPR sensing characteristics that are advantageous for the analyses of cellular bindings and technical compatibility with relatively low-cost telecommunication-grade measurement devices. In this work, we take consider their numerous assets to figure out their ability to selectively detect intact epithelial cells as analytes in cell suspensions in the range of 2-5 × 10(6) cells mL(-1). For this, the probe was first thermally annealed to ensure a strong adhesion of the metallic coating to the fiber surface. Its surface was then functionalized with specific monoclonal antibodies via alkanethiol self-assembled monolayers (SAMs) against extracellular domain of epidermal growth factor receptors (EGFRs) and characterized by peak force tapping atomic force microscopy. A differential diagnosis has been demonstrated between two model systems. The developed immunosensors were able to monitor, in real time, the specific attachment of single intact cells in concentrations from 3 × 10(6) cells mL(-1). Such results confirm that the developed probe fits the lab-on-fiber technology and has the potential to be used as a disposable device for in situ and real-time clinical diagnosis.

A super continuum characterized high-precision SPR fiber optic sensor for refractometry

Here we introduce a high sensitive side-polished fiber optic based surface plasmon resonance (SPR) sensor for refractometry in liquids for 1.32–1.37 Refractive Index Unit (RIU). In fabrication, a Controllable Hybrid Polishing Method (CHPM) was used to make high quality D-shaped fibers. For characterization, a super continuum (SC) light source was used in the measurement setup. The sensor has a spectral sensitivity of 5200nm/RIU with a Limit of Detection (LOD) of 5.8×10−6 RIU. Also, we have demonstrated that by reducing the intensity noise in our light source, a Signal-to-Noise Ratio (SNR) of 12.6dB and a Limit of Detection (LOD) of 3.7×10−6 RIU is achievable in an intensiometric approach.

Tapered Fiber-Optic Based Surface Plasmon Resonance Sensor

We propose a tapered fiber-optic based surface plasmon resonance (SPR) sensor. The plasmonic sensing is designed by coating the waist of tapered fiber-optic with gold. The transmission spectrum of SPR wavelength were investigated by 2D finite element method (FEM). The calculation shows that the dips of the resonance wavelength shift toward long wave direction with the thickness of gold film decreasing. And increasing the diameters of the waist core of tapered fiber-optic also makes the resonance wavelength shift long wave direction. Furthermore, changing the refractive index of the external samples from 1.333 to 1.343 with step of ~0.002, the SPR wavelength shifts linearly from 575.05nm to 472.5nm. Owing to its compact and simple configuration, it also provides a feasible program for the refractive index high sensitivity detection.Keywords: surface plasmon resonance (SPR); tapered fiber-optic sensor; surface plasma; finite element method (FEM); optical fiber sensor

Affinity based glucose measurement using fiber optic surface plasmon resonance sensor with surface modification by borate polymer

An affinity based method of glucose measurement using a fiber optic surface plasmon resonance (FO-SPR) sensor with surface modification by a borate polymer was proposed. In this method, the sensor is able to obtain the glucose concentration by detecting the surface refractive index of the sensor, which could avoid the impact of bioelectricity from viable tissues when applied for implantable measurement. A biocompatible borate polymer, PAA-ran-PAAPBA, which is capable of associating and dissociating with glucose molecules dynamically, performed non-consumption measurement of glucose, thereby enabling the possibility of glucose detection in hypoglycemic situations. Numerical simulation was performed based on the FO-SPR theory, and an online-transmission FO-SPR sensor with optimized structural parameters was fabricated. PAA-ran-PAAPBA was synthesized and immobilized onto the surface of the FO-SPR sensor using layer-by-layer self-assembly technique. An experimental system was built, and contrast-measurement experiment for 1–10 and 10–300mg/dL glucose solutions was performed; the FO-SPR sensor bonded with the borate polymer exhibited higher accuracy, especially for low-concentration detection. This study laid a technical foundation for further exploration of implantable measurement systems for blood glucose.